The invention relates to a vortex mixing apparatus in which a fluid, usually a liquid, is passed with a pulsatile, and preferably reversing, flow, but with a mean flow, through a conduit which has a configuration which causes vortices to be set up in the fluid.
An example of such an apparatus, for effecting the transfer of heat or mass from a primary channel to a secondary channel through a transfer membrane, is shown in our WO 88/04318. In such apparatus, a vortex mixing unit houses the heat or mass transfer membrane which separates the two channels and is provided with an array of hollows in its surface facing into the primary channel. Pumping diaphragms, in communication with the primary channel are provided at each end of the unit and are engaged by respective reciprocating pistons of a driving device. As a result one fluid passing through the primary channel is caused to form transient vortices, as described in GB-A-1442754, which enhances contact between the one fluid and the membrane.
The production of vortices in a liquid in a vortex mixing unit may also be used to promote thorough mixing of the components of a fluid, for example to promote a chemical reaction between components; or to promote contact between the fluid and a component such as an affinity ligand immobilised on a support.
If the vortex mixing apparatus has a removable mixing unit with pumping diaphragms at each end, it has been appreciated by the inventors that problems arise during the loading and unloading of the unit. For efficient pumping of the diaphragms by the pistons, each piston must reciprocate between a retracted position clear of the mixing unit housing and an extended position in which it compresses its respective diaphragm, but such that the mean point of the reciprocation is situated within the unit housing. Removal or insertion of the unit into the apparatus is then hampered by interference from the pistons, since the mean separation of the pistons is smaller than the gap required for the unit to pass through. Thus, to load or unload a unit is difficult, particularly for an unskilled operator.